Process for preparing 2,3,6-trimethylbenzoquinone

ABSTRACT

2,3,6-Trimethylbenzoquinone is prepared by reacting pseudocumene with a weak peracid having a pKa above 7.0 in the presence of a strong acid having a pKa below 3.0 or a Lewis acid.

United States Patent [1 1 Ohnishi et al.

Nov. 5, 1974 PROCESS FOR PREPARING 2,3,6-TRIMETHYLBENZOQUINONE Inventors: l-lajime Ohnishi; Yuji Nakazawa,

both of Saitama, Japan Assignee: Daicel Ltd., Osaka, Japan Filed: Sept. 13, 1973 Appl. No.: 396,827

us. cl 260/396 R int. Cl. C07C 49/64 Field Of Search 260/396 R I References Cited UNITED STATES PATENTS 8/1957 Phillips .f. 260/396 R Primary Examiner-Vivian Garner Attorney, Agent, or FirmW0odhams, Blanchard and Flynn [57] ABSTRACT 7 Claims, No Drawings R C SSFQR RIN 2,3,6-TRIMETHYLBENZOQUINONE BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a process for preparing 2,3,o-trimethylbenzoquinone by a simplified procedure in which pseudocumene is oxidized with a peracid solution in the presence of an acid catalyst.

2. Description of the Prior Art 2,3,6-Trimethylbenzoquinone can be reduced to 2 ,3,o-trimethylhydroquinone, which is known to be an important starting material for the synthesis of vitamin E. Although various processes for preparing 2,3,6-trimethylbenzoquinone have been proposed, many of them have been not advantageous from a commercial viewpoint, because they require either starting materials which are not readily available, or a complicated unit reaction procedure or special reagents. For example, a known process wherein pseudocumene is used as a starting material requires a series of unit reaction procedures in a step of introducing hydroxyl groups into the nucleus, i.e., sulfonation or bromination followed bynitration, reduction and oxidation, even though the starting material is readily available. In addition, according-to this process, a large amount of by-products are formed and thesteps are complicated and lengthy.

R. D. Chamber, et al, proposed in J. Chem. Soc. 1804 (1959) a process for obtaining 2,3,6-trimethylbenzoquinone from pseudocumene by the use of trifluoroperacetic acid. However, there has not been reported a process for preparing 2,3,6-trimethylbenzoquinone from pseudocumene by using a peracid weaker than trifluoroperacetic acid, for example, peracetic acid or perpropionic acid, as shown in Table I.

Table I Acid Peracetic acid Perpropionic acid Perbutyric acid Monochloroperacetic acid Perbenzoic acid Perphthalic acid Performic acid Trifluoroperacetic acid SUMMARY OF THE INVENTION This invention relates to a process for preparing 2,3,6-trimethylbenzoquinone, characterized in that pseudocumene is oxidized with a weak peracid in the presence of an acid catalyst to obtain 2,3,6-trimethylbenzoquinone by a one step reaction.

The purpose of the present invention can be attained by using a stable peracid such as peracetic acid, instead of using an expensive and corrosive peracid such as trifluoropcracetic acid, in the presence of a strong acid of a pKa below 3.0 or a Lewis acid as catalyst.

If pseudocumeneand peracetic acid are reacted in the absence of acid catalyst, the desired product 2,3,o-trimethylbenzoquinone is obtained in only a trace r of pseudocumene.

perphthalic acid as shown in Table l. The amount of the peracid employed is l to 10 moles, preferably 2 to 5 moles, per mole of pseudocumene.

The catalyst usedin the present invention is a strong acid having a pKa of less than 3.0 or a Lewis acid. As strong acids, there may be mentioned, for example, perchloric acid, periodic acid, sulfuric acid, nitric acid, p-toluenesulfonic acid, phosphoric acid, phosphorous acid and fluoroboric acid. As Lewis acids, there may be mentioned for example, boron trifluoride, mercuric chloride and zinc chloride. A mixture of these acids can also be used. The catalyst is used in an amount of l to 150 wt. percent, preferably 3 to 20 wt. percent, based on the weight of pseudocumene.

In carrying out the process of the present invention, the use of a solvent is preferred. Particularly, the selectivity can be increased-remarkably if a lower carboxylic acid such as acetic acid, propionic acid or butyric acid, or a chlorinated hydrocarbon such as chlorobenzene, dichloromethane, chloroform, carbon tetrachloride, trichloroethylene or tetrachloroethyleneis used. The amount of the solvent is from 3 to 20 times the weight The process of the present invention is carried out at a temperature such that the reaction is accelerated while the peracid does not become unstable, usually at 0 to C. The reaction time varies depending on the reaction temperature. i t

The process of the present invention will be further described by reference to illustrative examples, which by no means limit the invention. I

.The results of the reaction were evaluated in the following manner;

r The crude reaction liquid is subjected to an extraction with benzene/water, the extract is subjected to steam distillation todistill out 2,3,6-trimethylbenzoquinone. The product is extracted again with benzene. The extract is concentrated andhydrogenated in thepresence of a Pd-C catalyst (5 percent palladium carried on active carbon; a product of NipponEngelhard, Limited) to isolate 2,3,6 trimethylhydroquinone. The result is shown by yield (g) of 2,3,6-trimethylhydroquinone.

' EXAMPLES 1 7 In a four-neck flask provided with a thermometer, stirrer, reflux condenser and dropping funnel, 25 parts of acetic acid as solvent, 6 parts of pseudocumene and a catalyst in an amount shown in the following table were charged. The temperature was regulated to be 50C. 38 parts of peracetic acid solution (1:2 mixed solution of acetic acid and ethyl acetate containing 19 percent of peracetic acid) were charged in the dropping funnel and dropped slowly into the reactor. The reaction was carried out ata temperature kept at 50C for a period shown in the following table to obtain the result shown in the same table.

TABLE II 8 Example 1 2 3 4 5 7 Catalyst None H 50 HClO PTS HBF., BF HgCl Amount of catalyst (part) 0.7 0.7 0.7 0.7 0.35 0.7 Reaction time (hr.) l3 ll 12 l2 l2 l2 l2 TMBQ Selectivity (71) Trace 9.9 14.3 6.1 8. 7.6 8.9

PTS p-toluenesulfonic acid TMBQ: 2,3,6-trimethylbenzoquinone Selectivity (70) is shown by molar of resulting 2,3,6-trimethyl benzoquinone based on pseudocumene consumed.

EXAMPLES 8 l4 EXAMPLE 17 In a four-neck flask provided with a thermometer, stirrer, reflux condenser and dropping funnel, 60 parts The procedure of Example 15 was repeated by using 20 percent perbenzoic acid solution. More particularly,

O ps o 7 Parts Of perc oric acid and l 12 parts of pseudocumene and 4.4 parts of 70 percent parts of a solvent were charged. 380 parts of peracetl perchloric acid solution were charged in a reactor. 207 301d Solution Solution of 396116 9 f ethyl parts of 20 percent perbenzoic acid solution (chlorollcetatc containing 19 Percent of peracetic 991d) were form solution containing 20 percent of perbenzoic dropped therein slo ly through the dropplng funnel acid)were dropped therein slowly under cooling. Tem- WhllE temPeraturc kept at a predeteimmd Value 20 perature was elevated slowly under stirring and the reas shown 1n the following table. The reaction tlme was action was carried out at for hours The Show m l table The resultspfEthe i amounts of converted perbenzoic acid and pseudocul eva uate m t 6 Same manner as m Xamp es mene were 95.3 percent and 53.8 percent, respectively.

Table 111 Example 8 9 10 ll 12 l3 l4 Solvent initially None Acetic Propionic Chloro- Dichloro- Chloro- Carbon charged acid acid benzene methane form tetra chloride Reaction temperature (C) 60 50 60 50 60 60 60 Reaction time (hr.) 6 l2 6 l2 6 7 6 TM 80 selectivity 71.) 5.9 12.7 13.8 12.6 18.6 17.6 16.6

EXAMPLE 15 The yield'of 2,3,6-trimethylbenzoquinone based on the In the same reactor as above, 50 parts of chloroform converted pseudocumene was Percentas reaction solvent, l2 'parts of pseudocumene and 2.7 parts of 70 percent perchloric acid solution as catalyst EXAMPLE 18 were charged. 76 parts of 30 percent peracetic acid solution (mixed solution of acetic acid and ethyl acetate In m reactcr as above parts of acetlc acld as react1on solvent, 12 parts of pseudocumene and 15 contaimng 30 percent of peracetic acid) were dropped arts of nitri acid as 0 ml t h d Th t slowly through a dropping funnel. The reaction was 45 p t c l Yg z arge carried out for 7 hours while the reaction temperature pera was regu ate e part? 0 r was kept at 0 The amounts of converted peracetic cent peracet1c acld solut1on (rn1xed solution of acetic acid and pseudocumene were 87.6 percent-and 50.2 aclcland ethyl acetate comamlng P of P percent, respectively. The yield of 2,3,6-trimethylbenacetlc acld) dropped l y through a pp f zoquinone based on the amount f consumed 5O funnel. The reactlon was carried out for 11 hours while pseudocumene was 5 percent. the reaction temperature was kept at 60C. The

amounts of converted peracet1c acid and pseudocu- EXAMPLE 16 mene were 93.9 percent and 56.8 percent, respectively. The procedure of Example 15 was repeated by using The yleld of 2,3,6-tr1methylbenzoqu1none based on the 25 percent perpropionic acid solution More particw amount of consumed pseudocumene was 25.4 percent. larly, 50 parts of chloroform, 12 parts of pseudocumene and 3.4 parts of 70 percent perchloric acid solu- EXAMPLE 19 lion as Catalyst i? 1 8 9 a j P 9 p of In the same reactor as above, 50 parts of acetic acid 25 P P P P acld (P P P 4 Solution as reaction solvent, 6 parts of pseudocumene, 0.6 part containing 25 percent of perpropionic ci were of concentrated sulfuric acid and 0.6 part of phosdropped therein slowly through a dropping funnel. The phoric acid as catalyst were charged. The temperature reaction was carried out for 7 hours while the reaction was regulated to be 70C. 47. parts of 24.3 percent pertemperature was kept at 60C. The amounts of conacetic acid solution (mixed solution of acetic acid and verted perpropionic acid and pseudocumene were 81.3 ethyl acetate containing 24.3 percent of peracetic acid) percent and 46.9 percent, respectively. The yield of 2,3,6-trimethylbenzoquinone based on the consumed amount of pseudocumene was 23.6 percent.

were dropped slowly through a dropping funnel. The reaction was carried out for 6 hours while the reaction temperature was kept at C. The amounts of converted peracetic acid and pseudocumene were 92.5 percent and 23.3 percent, respectively. The yield of 2,3,6-trimethylbenzoquinone based on the amount of consumed pseudocumene was 44.6 percent.

EXAMPLE 20 In the same reactor as above, 50 parts of acetic acid as reaction solvent, 12 parts of pseudocumene, 1.2 parts of 70 percent perchloric acid solution and 1.2 parts of phosphoric acid as catalyst were charged. The temperature was regulated to be 70C. 94 parts of 24.3 percent peracetic acid solution (mixed solution of acetic acid and ethyl acetate containing 24.3 percent of peracetic acid) were dropped slowly through a dropping funnel. The reaction was carried out for 9 hours while the reaction temperature was kept at 70C. The amounts of converted peracetic acid and pseudocumene were 93.6 percent and 45.2 percent, respectively. The yield of 2,3,6-trimethylbenzoquinone based on the amount of consumed pseudocumene was 35.3 percent.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process for preparing 2,3,6-trimethylbenzoquinone which comprises reacting pseudocumene with a peracid of pKa of more than 7.0 at a molar ratio of pseudocumene/peracid of l/l to 10, in the presence of from 1 to 150 percent by weight, based on the weight of pseudocumene, of an acid catalyst selected from the group consisting of strong acids of pKa of less than 3.0 and Lewis acids, at a temperature of from zero to C.

2. A process according to claim 1, in which the peracid is selected from the group consisting of peracetic acid, perpropionic acid, perbutyric acid, monochlorperacetic acid, perbenzoic acid, perphthalic acid and performic acid.

3. A process according to claim 2, in which the molar ratio of pseudocumene/peracid is from V: to 5.

4. A process according to claim '1, in which said acid catalyst is selected from the group consisting of perchloric acid, periodic acid, sulfuric acid, nitric acid, p-toluene-sulfonic acid, phosphoric acid, phosphorous acid, boron triluoride, fluoroboric acid, mercuric chloride, zinc chloride and mixtures thereof.

5. A process according to claim 4, in which the amount of acid catalyst is from 3 to 20 percent by weight, based on the weight of pseudocumene.

6. A process according to claim 1, in which the pseudocumene is dissolved in 3 to 20 times its weight of a solvent selected from the group consisting of lower carboxylic acids and chlorinated hydrocarbons.

7. A process according to claim 6, in which the solvent is selected from the group consisting of acetic acid, propionic acid, butyric acid, chlorobenzene, dichloromethane, chloroform, carbon tetrachloride, trichloroethylene and'tetrachloroethylene. 

1. A PROCESS FOR PREPARING 2,3,6-TRIMETHYLBENZOQUINONE WHICH COMPRISES REACTING PSEUDOCUMMENE WITH A PERACID OF PKA OF MORE THAN 7.0 AT A MOLAR RATIO OF PSEUDOCUMENE PERACID OF 1 1 TO 10, IN THE PRESENCE OF FROM 1 TO 150 PERCENT BY WEIGHT, BASED ON THE WEIGHT OF PSEUDOCUMENE, OF AN ACID CATALYST SELECTED FROM THE GROUP CONSISTING OF STRONG ACIDS OF PKA OF LESS THAN 3.0 AND LEWIS ACIDS, AT A TEMPERATURE OF FROM ZERO TO 100*C.
 2. A process according to claim 1, in which the peracid is selected from the group consisting of peracetic acid, perpropionic acid, perbutyric acid, monochlorperacetic acid, perbenzoic acid, perphthalic acid and performic acid.
 3. A process according to claim 2, in which the molar ratio of pseudocumene/peracid is from 1/2 to
 5. 4. A process according to claim 1, in which said acid catalyst is selected from the group consisting of perchloric acid, periodic acid, sulfuric acid, nitric acid, p-toluene-sulfonic acid, phosphoric acid, phosphorous acid, boron triluoride, fluoroboric acid, mercuric chloride, zinc chloride and mixtures thereof.
 5. A process according to claim 4, in which the amount of acid catalyst is from 3 to 20 percent by weight, based on the weight of pseudocumene.
 6. A process according to claim 1, in which the pseudocumene is dissolved in 3 to 20 times its weight of a solvent selected from the group consisting of lower carboxylic acids and chlorinated hydrocarbons.
 7. A process according to claim 6, in which the solvent is selected from the group consisting of acetic acid, propionic acid, butyric acid, chlorobenzene, dichloromethane, chloroform, carbon tetrachloride, trichloroethylene and tetrachloroethylene. 